Guinevere

The daughter of King Leodegrance. She married Artoria to bring about the outward appearance of a kingdom in Britain.
Though she respected and admired Artoria, and tried her best to imitate her way of life, in the end she was simply too much of a “normal woman” to keep up.
I dare say she was a glasses-wearing girl at heart. You know, the stereotypical kind that's actually really hot when she takes them off.
In accordance with the culture of the time, she was taught from a young age to avoid self-reflection, and so had very little sense of herself as a woman, or even that there was a difference between the sexes. She truly thought that the relationship between a king and queen was something formed solely from ideals. She never could have imagined that a different sort of attraction between people could exist at all. But, that all changed when she met Sir Lancelot.
From that day on she was cast into turmoil, torn between the “tsun” of her conviction and the “dere” of her soul, until finally both she and Lancelot were driven into a predicament from which there was no escape. Such was the fate of a tsundere who risked her life in troubled times. Geez, Camelot was hell, huh? Bahahaha!

Fate/Zero material: Fate/Zero Encylopedia